This invention generally relates to vulcanizing flexible elastomeric materials or compositions and the like and concerns an apparatus for vulcanizing flexible roofing materials such as a rubber membrane or sheet.
It is to be understood that the expression "vulcanizing" means subjecting an unvulcanized product to elevated temperatures and elevated pressures for a period of time sufficient as to cause development of a cross-linked integral molecular structure.
Various forms of vulcanizing apparatus and methods of vulcanizing have been developed for use in the manufacture of a wide variety of products. Illustrative of these vulcanizing units are U.S. Pat. No. 4,199,542 issued in the name of Challer E. Taylor describing a method and apparatus for continuously vulcanizing hose product, U.S. Pat. No. 2,550,183 issued in the name of H. A. Bourne setting forth an apparatus for molding V-belts and U.S. Pat. No. 1,368,679 issued in the name of A. Adamson which discloses a conventional vulcanizing unit.
An established procedure for vulcanizing sheet products such, for example, as a flexible rubber roofing membrane, has been to calendar sheet material in 4 feet by 20 feet sections to form large sheets, e.g., 48 feet by 20 feet (utilizing 13 sections) or 100 feet by 20 feet (using 25 sections). The 4 feet by 20 feet sections are adhered along their length with corresponding edges being lapped or abutted. The resultant large sheet is then wrapped about a mandrel with talc dusted between sheet layers to prevent the vulcanized sheet from adhering together. A series of such identically formed sheets are wrapped about identical individual mandrels which are fitted into a vulcanizing chamber for treatment. The mandrels are placed side by side within the vulcanizing chamber on a series of vertically spaced horizontal supports. However, the resulting arrangement does not efficiently use the available space within the vulcanizing chamber, and as a result, a greater amount of energy is expanded than necessary to cure the sheet material with concomitant increased labor and handling.
The above described conventional practice is unnecessarily expensive in view of the labor and manufacturing costs and inefficiencies, particularly with regard to seaming the smaller sections into large sheets and to the loading of the large sheets onto the mandrels. Moreover, a high percentage of sheets contain deformations, bumps, rips or noticeable seams when manufactured in accordance with conventional techniques.
As a result, it is desirable to develop a process which not only reduces manufacturing costs and labor, but is more efficient and eliminates deformations to produce a high quality uniform sheet. Additionally, conventional vulcanizing methods do not provide means for removing talc from between wrapped layers of the sheets. The talc residue must be removed before use or installation so that adhesive gum tapes and other materials will adhere to the surface of the sheet. Currently, talc is removed by washing sheets with solvents and other laborious methods of cleaning after removing the sheets from the vulcanizing chamber.